The Power of the Rings: The GRB 221009A Soft X-Ray Emission from Its Dust-scattering Halo

Abstract

GRB 221009A is the brightest gamma-ray burst (GRB) ever detected that has occurred at low Galactic latitude. Owing to this exceptional combination, its prompt X-ray emission could be detected for weeks in the form of expanding X-ray rings produced by scattering in Galactic dust clouds. We report on the analysis of 20 rings, generated by dust at distances ranging from 0.3 to 18.6 kpc, detected during two X‐ray Multi Mirror (XMM)-Newton observations performed about 2 and 5 days after the GRB. By fitting the spectra of the rings with different models for the dust composition and grain size distribution, we reconstructed the spectrum of the GRB prompt emission in the 0.7–4 keV energy range as an absorbed power law with photon index Γ = 1–1.4 and absorption in the host galaxy N H,z = (4.1–5.3) × 1021 cm−2. Taking into account the systematic uncertainties regarding the column density of dust contained in the clouds producing the rings, the 0.5–5 keV fluence of GRB 221009A can be constrained between 10−3 and 7 × 10−3 erg cm−2. Both the fluence and the photon index indicate the presence of a possible soft excess with respect to the extrapolation of the main GRB peak observed at higher energies.

XMM-Newton and INTEGRAL Observations of the Bright GRB 230307A: Vanishing of the Local Absorption and Limits on the Dust in the Magellanic Bridge

“…However, we note that the results depend on the chosen dust model. As an example, adopting the BARE-GR-B model of Zubko et al (2004), which provided the best fit in other observations of X-ray halos and rings produced by dust scattering (e.g., Smith et al 2006;Tiengo et al 2010Tiengo et al , 2023, we can limit the quantity of dust in this part of the Magellanic Bridge to A V < 0.25-0.32. Even so, these limits are more constraining than the total reddening E(B − V ) = 0.08 ± 0.08 reported in the map of Chen et al (2022), which in this direction has a spatial resolution of ¢ 55 and estimates the same reddening value also for foreground Galactic stars.…”

“…GRB 230307A is also interesting because it occurred in the direction of the Magellanic Bridge, a structure consisting mainly of H I, which connects the Small and Large Magellanic Clouds and was probably produced by the tidal interaction between these two galaxies (see, e.g., Gaia Collaboration et al 2021, and references therein). The occurrence of a bright GRB in this direction offers the possibility to constrain the poorly known properties of the interstellar dust in the Bridge through the analysis of scattered X-ray radiation, as done for Galactic dust clouds with other GRBs (Vaughan et al 2004(Vaughan et al , 2006Tiengo & Mereghetti 2006;Vianello et al 2007;Pintore et al 2017;Tiengo et al 2023).…”

GRANDMA and HXMT Observations of GRB 221009A: The Standard Luminosity Afterglow of a Hyperluminous Gamma-Ray Burst—In Gedenken an David Alexander Kann

“…Observations with IXPE (Negro et al 2023) confirm the most distant dust ring found by Swift at 3.75 ± 0.0375 kpc and report an even more distant dust curtain at 14.41 ± 0.865 kpc. Recently, Vasilopoulos et al (2023) reported a detailed analysis of Swift XRT data and also found evidence for dust out to 15 kpc (see Williams et al 2023 for further analysis), and XMM-Newton analysis of a total of 20 dust rings presented by Tiengo et al (2023) detects an even further dust curtain at ≈18.6 kpc.…”

“…The HXMT/LE flux measurements are not corrected for the dust echo scattering (see, for example, Negro et al 2023;Tiengo et al 2023;Williams et al 2023), since Insight-HXMT is a collimated telescope with a large FoV, e.g., 1°× 4°. It is thus not possible to easily remove the dust echo scattering flux contribution.…”

A Sensitive Search for Supernova Emission Associated with the Extremely Energetic and Nearby GRB 221009A

“…We note that there are varying interpretations of the intrinsic extinction and hydrogen column density of the host that are model dependent on the spectral shape of the afterglow (e.g., Tiengo et al 2023). However, we believe that the most likely physically plausible situation is the first where E(B − V ) host is allowed to vary freely between 0.3 and 0.5 mag, due to the possibility of a significant amount of intrinsic hydrogen column density in the host that may be up to N H ≈ 1.29 × 10 22 cm −2 (Williams et al 2023).…”